1. Field of the Invention
The present invention relates generally to sorbent materials and process for the manufacture thereof; and more particularly to an effective sorbent for either water or land recovery of oil spills which allows for the option of: i) recovery of the oil and reuse of the sorbent, ii) use of sorbent and oil as a fuel, or, iii) with the addition of suitable microbes, bioremediation of the oil.
2. Description of the Prior Art
Accidental oil spills, whether on land or water, are a source of concern for the entire planet. Oil slicks on the surface of open bodies of water may result from accidental spills when a ship is being fueled; when a tanker is being loaded or unloaded; or when a tanker is wrecked and breaks up on the high seas. In some instances, oil appears on the surface of the water in rivers or ports when oil-carrying storage tanks are flushed with water. Oil slicks may also occur when leaks, fires, or explosions are encountered during offshore drilling operations.
When an oil spill occurs, the oil is carried by tides, currents and winds to adjacent shore lines where it fouls beaches, kills marine animal life and plant life and adversely affects boating, bathing, fishing, and drinking water. When oil slicks develop around loading docks, ship yards, offshore drilling platforms, barges and piers, the fire potential is very serious, and in the event a slick should be ignited, the resulting fire may cause loss of life as well as property and materials. The major oil spills of recent years, wherein millions of gallons of oil have been abruptly dumped into the ocean, have magnified the need for rapid and effective means of containment.
Land is not immune from oil spills of all kinds. When a tractor-trailer carrying oil products turns over on an interstate highway in the middle of a city or a home heating oil delivery person dumps a couple of hundred gallons of oil in a basement by mistake, the resulting potential for fire, pollution, and loss of life or property is no less real than if the accident had happened at sea. In areas that have a fragile water supply system, the threat of an oil spill that could destroy the water source is a real concern.
Once an oil spill occurs, pollution damage begins immediately and is magnified many times as the oil disperses, especially as it is washed ashore in the case of a spill on a waterway. Of the millions of dollars which are spent on the cleanup of oil spills, the major part is devoted to cosmetic purposes, cleaning up the oil after the major damage has been done. Dramatic savings are realized if the oil can be contained and the damage arrested at the scene of remediation, including pickup and the spill.
Various methods have been employed to cope with oil spills; however, such prior art methods suffer from a number of disadvantages. In all instances of oil spills, it is desirable to achieve a number of site and circumstance specific objectives. Oil spills on land are most commonly picked up with inexpensive clay based materials and other low cost inorganic sorbents. If oil pickup is in an industrial environment, such as on industrial floors or on walkways, often the only consideration is the lowest possible cost sorbent. However, in other instances it must also be non-abrasive to machinery. If oil pickup is on exposed ground, it may be desirable or required for the unused residual sorbent to be biodegradable and safe to humans, plants, animals, and the environment. When the used oil saturated sorbent is to be disposed of in a landfill or when there will be concern about the possible harmful effects of used oil saturated sorbent remaining in the environment at the spill site, it may be necessary or desirable to remediate the used oil saturated sorbent with a separate step of final remediation by introducing oil digesting microbes. In the instance of oil spills occurring on land that require fast response or in locations difficult to reach by vehicle, the sorbent of choice should be as light and compact as possible to facilitate transfer by personnel on foot. That situation requires a sorbent with a high pickup-to-weight ratio plus high oil containment capability. For oil spills on water, the sorbent of choice should be a lightweight, floating sorbent material that can be used loose or in pads, socks, pillows, booms, or as an oil extracting and water rejecting filter element that ideally would pickup the oil without contamination by water. The sorbent Of choice for oil spills on water should also be compressible and reusable to enable extraction of the oil in a condition such that the oil and also the sorbent is reusable, and uncontaminated by water. It is often desirable for the sorbent of choice for oil spills on water to be biodegradable and safe to shellfish, aquatic plants, or any aquatic life, and especially not to contain any plastics or toxic ingredients.
In many instances the used saturated sorbent will be desired for use as fuel to be burned to recover the available energy, and as such, it must be low in ash content and without any ingredients that contribute harmful or undesirable products of combustion.
If large quantities of sorbent are going to be stored or stockpiled, it is desirable that the unused sorbent not support combustion, thereby providing an extra measure of safety both during the manufacturing process as well as in distribution and storage. It is also desirable for a sorbent to be easily identified by a unique colorant so as not to be confused with something of potentially similar appearance when in the field or when not in a labeled container.
To facilitate the lowest possible cost the sorbent should require very low energy to manufacture with simple low cost machinery and extremely low cost raw materials, preferably of benign industrial or municipal waste raw materials that are in abundant supply at present and in the foreseeable future. It is also desirable for the ideal sorbent to have the capability of remediating a wide range of liquid spills other than just oils or hydrocarbons, i.e., synthetic oils and fuels, coolants, paints, polymers, alcohols, blood and plasma, pharmaceuticals, sewage, solvents, oils with PCB's, aromatics, chromates, cyanides, sulfides, insecticides, and herbicides.
The present state of the art requires making a choice of the sorbent to be used for each circumstance from among a large number of types of sorbent materials available. Dramatic savings are available with the advantages of having one low cost sorbent that will accomplish all these important objectives of spill remediation. This would obviate having to inventory a wide variety of sorbents for their different uses. Within the prior state of art there is no singular composition of matter that achieves all these important objectives.
In some of the prior art, sorbent materials such as sawdust, peat fibers, diatomaceous earth, expanded perlite or vermiculite, and the like, have been used to spread upon an oil slick in order to soak up the oil. In other prior art, sorbents such as the above are used in combination with other reagents to clean up oil spills. For example, in U.S. Pat. No. 5,035,804, Stowe teaches combining perlite, vermiculite, or sand with a hydrophobic/oleophilic coating of sulfur, a metallic sulfate, an alkali metal nitrate, and burned hydrocarbon oil. Some of these compounds sink when the oil is sorbed effectively shifting the pollution from the water surface to the ocean or river bottom. The process of recovery of the oil is time consuming and relatively expensive using this invention.
In U.S. Pat. No. 5,037,557, Warrenchak et al. teach a method of sorbing hydrocarbons from water using treated, fumed silica. The oil picked up by this invention is from 1 to 10 times the weight of the treated silica. However, if less than an excess of silica is used, the resulting globules are tacky and difficult to screen off. Thus, 100 gallons of oil may require 120 to 180 pounds of treated, fumed silica to capture the oil successfully.
Heretofore clay-based materials and other inorganic sorbents have been utilized in the control and removal of undesired liquids from industrial floors and walkways and similar industrial environments. But, such materials are not sufficiently effective as determined by sorptive capacity; not convenient as determined by bulk density, typically 25 to 40 lbs./ft.sup.3 ; and not readily decomposable or degradable, as the wholly inorganic constituents preclude incineration even when saturated with combustible liquid material or the like. A recent advance in sorptive media entails the pelletization of cellulose fibers and clay and/or other inorganic solids as disclosed in U.S. Pat. No. 4,374,794 by Kok. However, the action of pelletizing a combination of cellulose fibers and inorganic solids or "fibers" requires use of considerable force applied to the material in order to extrude it form a die orifice. The requisite force is a compressive action that eliminates interstitial spaces in the body of the pellet, creates a non-porous surface, creates a dimensionally stable cylindrical shape, and results in a product having a bulk density typically ranging from 25 to 40 lbs./ft.sup.3. Moreover, when used as an absorptive media on floor surfaces, the extruded pellets present a hazardous interface between the floor surface and pedestrian traffic. Further, such extruded pellets exhibit low absorptive capacities.
Each particular sorbent or class of sorbents presents its own difficulties. The inability of many sorbents to resist sorption of water is a very serious limitation considering that the most serious oil clean-up operations involve discharge of oil in seas or other bodies of water. Attempts in the past to impart the requisite hydrophobicity to oil sorbents, even where some success was obtained, have resulted in a sorbent whose cost is prohibitive.
A difficulty with materials which are mere sorbents is that they are sorbents for both water and oil, so that a large part of the sorptive capacity of the particles is consumed by saturation with water and is unavailable for pick-up of the oil. For example, oil-water emulsions which are used as cutting fluids require separation of oil from the water prior to disposal.
Oil spills occurring at sea, in lakes, in rivers, and streams present a special problem. In order to remove hydrocarbons from water effectively, it is necessary that the sorbent sorb only the hydrocarbon and not the water. That is, the material should be both oleophilic and hydrophobic. Therefore, in other prior art, efforts have been made to coat or otherwise modify the sorbents to enhance their selectivity for oil over water. U.S. Pat. No. 4,670,156 by Grenthe discloses the use of fibrous cellulosic material, e.g. sulphite reject, which is subjected to forced heating to enhance hydrophobic and oleophilic properties. However, the absorption ratio is only 3 or 4 to 1. After a few days the material loses its hydrophobic characteristic to the extent it will sink in water, and the cost of manufacturing is higher.
Another patent of interest is one recently issued to Papyrus Kopparfors A.B. of Molndal, Sweden as the assignee of Thomas Ericsson, U.S. Pat. No. 4,537,877. Ericsson discloses various examples of a particulate oil sorbing composition comprising at least 50 percent by weight hydrophobic cellulose pulp fibers" . . . blending with at least 30 percent up to 50 percent of an inorganic cellulose paper pulp filler . . . ". Unfortunately, the inclusion of large amounts of inorganic cellulose paper pulp fillers--including particularly amounts in the range proposed by Ericsson comprising at least 30 percent by weight and ranging up to 50 percent by weight of the basic composition--present a number of problems. First and foremost, the inorganic solids or "fillers" tend to increase the bulk density of the resulting product which generally ranges from 16 to 20 lbs/ft.sup.3 ; and, as a consequence, even though the product is hydrophobic, upon saturation with oil it will not float. Moreover, the large amount of inorganic solids present tends to reduce both the rate of absorption and the absorptive capacity of the product produced. Additionally, the inorganic solids are not readily flammable and/or degradable. These inorganic solids cannot be satisfactorily disposed of by incineration, thus producing a significant quantity of non-degradable ash, which creates a high-cost disposal problem, and reducing the amount of heat that can be generated per cubic volume of material. Phillips (below) reports Ericsson's invention leaves 44 percent ash after incineration. The inorganic solids present further create significant dust problems resulting in eye and/or breathing irritants and undesirable abrasion of production equipment.
Phillips in U.S. Pat. Nos. 4,931,139 and 5,091,245 teaches a cellulose substrate absorbent with an inorganic solids content of not more than 30 percent dry weight. The absorption capacity is just over 3 to 1 (301 percent by weight) after 16 hours. After an incineration test, there was only a 9.6 percent ash. Still a better pick-up ratio and ash content is desirable.
A particularly serious limitation of any and all sorbents of the prior art is the failure to specifically address the problem of environmental disposal of the sorbent once the oil has been sorbed. Nutrients and protection are necessary for microbes when they are included as a component for effective bioremediation of used sorbent when disposed of in the environment. To facilitate the most efficient microbial action, it may also be necessary to introduce both a system of protection of the microbes as well as introduction of microbial nutrients to enhance the microbial effectiveness, survival, and growth.
It would be advantageous to provide an improved single composition of matter in a sorbent that achieves all of the above objectives and which: is suitable on water and on land, is fire retardant, has a high pickup ratio (&gt;30 to 1), is not limited to use in any one form, can be used as a filter element to separate oil from water, is non-abrasive to machinery, and is simple, inexpensive, and effective. It would be further advantageous to have a sorbent that offers a choice of disposition of the used product: a sorbent which can be reused repeatedly after oil extraction by compression which facilitates 70 percent recovery of oil without contamination by water; used sorbent which can be burned as fuel to recover 100 percent of energy and contributes only 1 percent ash; or a sorbent in which microbes are included as a component for effective bioremediation of used sorbent if disposed of in the environment.